Process and catalyst for hydrocracking hydrocarbon oil

ABSTRACT

A CATALYST FOR HYDROCRACKING HYDROCARBON OILS COMPRISES AN IRON GROUP METAL AND FLUORINE INCORPORTED INTO AN AMORPHOUS ACID-ACTING REFRACTORY OXIDE, THE INCORPORATION BEING CARRIED OUT BY CONTACTING A HYDROGEL OF SAID REFRACTORY OXIDE WITH AN AQUEOUS SOLUTION OF AN IRON GROUP METAL COMPOUND, WASHING THE CONTACTED HYDROGEL AND CALCINING AT A TEMPERATURE OF ABOUT 800 TO 1200*F.

United States Patent 01 US. Cl. 252-459 3 Claims ABSTRACT OF THEDISCLOSURE A catalyst for hyddocracking hydrocarbon oils comprises aniron group metal and fluorine incorported into an amorphous acid-actingrefractory oxide, the incorporation being carried out by contacting ahydrogel of said refractory oxide with an aqueous solution of an irongroup metal compound, washing the contacted hydrogel and calcining at atemperature of about 800 to 1200 F.

This application is a continuation-in-part of application, Ser. No.393,735, filed Sept. 1, 1964, now abandoned, which is acontinuation-in-part of application, Ser. No. 184,947, filed April 4,1962 now abandoned.

This invention relates to a process for the catalytic conversion ofhydrocarbons. More particularly, this invention relates to thedestructive hydrogenation of hydrocarbons and improved catalyststherefor.

Destructive hydrogenation, more commonly called hydrocracking, bycatalytic means is old and well known to the art. Destructivehydrogenation of a hydrocarbon oil, usually a coal tar of a high-boilingpetroleum frac tion, such as gas oils or topped crude, generally iscarried out at quite high temperatures and pressures of the order of 850F. and 1500 p.s.i.g. and up. Catalysts for the destructive hydrogenationof oil are generally a combination of hydrogenation and crackingcatalysts. Of the hydrogenation catalysts, molybdenum and tungsten andthe oxides and sulfides thereof have generally been most favored. Thecracking catalyst has generally been an activated clay or syntheticsilica-alumina.

In a destructive hydrogenation process, high boiling oil feed is usuallyhydrogenated in a first stage and then hydrocracked in a second stage.Hydrogenation in the first stage must be suflicient to assure almostcomplete removal of nitrogen compounds, i.e., to below 5 parts permillion, in order for activity of the hydrocracking catalyst in thesecond stage to remain at ahigh level (see Progress in Hydrogenation ofCoal and Tar, by Kenneth Gordon, Chemical Age, volume 55, pages 795-804, Dec. 28, 1946). Hydrogenation to such an extremely low nitrogencontent adds greatly to the cost of the over-all hydrocracking process.Destructive hydrogenation processes have been used primarily in Europe,and have been little used by refiners in America because of their knownhigh cost, and because the catalysts have in general been low inactivity, highly susceptible to poisons such as nitrogen compounds, andhave a relatively poor life.

More recently, however, a hydrocracking process has been described whichis carried out at somewhat lower temperatures and pressures with acatalyst comprising nickel sulfide or cobalt sulfide deposited onsilica-alumina cracking catalyst. This process, as with the olderprocess, has the disadvantage that the catalyst is highly susceptible topoisons such as nitrogen compounds. Therefore, the high boilinghydrocarbon oil must be subjected to a severe pretreatment for theremoval of hoe nitrogen compounds such as pretreatment with acids,acidic ion-exchange resins or by severe catalytic hydrogenationtreatment. Moreover, even with an essentially nitrogen-free feed it isconsidered necessary to operate initially at a relatively lowtemperature for a period of time to achieve a long catalyst life.

An improved hydrocracking process has now been found which employs acatalyst markedly superior to those used heretofore. The catalyst of theprocess of the invention comprises an acid-acting refractory oxide and ametal of the iron group of Group VIII of the Periodic Table of Elements.A particularly active and improved catalyst comprises silica, alumina,an iron group metal, and a fluoride. The iron group metal is apparentlybound with the other components of the catalyst in such a manner that itis highly active and stable for hydrocracking high boiling oils and yetis less susceptible to poisons, such as nitrogen, which are generallypresent in such hydrocarbon oils. Of the iron group metals, nickelprovides a highly active catalyst for hydrocracking conversion and ispreferred for such conversions.

The catalyst is prepared by contacting a hydrogel of the acid-actingrefractory oxide substantially free from sodium (less than about 0.1% w.on a solids basis) with an aqueous solution of an iron group metalcompound. The iron group metal compound can be any suitablewater-soluble compounds, e.g. nitrates, wherein the iron group metal ispresent as a cation. For markedly active and stable catalysts of thisinvention, fluorine is incorporated into the hydrogel, preferably from acommon solution with the iron group metal. The iron group metal cationpresumably exchanges with cations in the hydrogel, for example, ammoniumions in the case of a hydrogel which has been washed with an ammoniumsalt to remove sodium ions, or is firmly bound in some manner within thegel, since metal is retained in the gel even when the metal-containinggel is washed with water to remove excess metal solution.

Thus, in accordance with the process of the present invention, ahydrocarbon distillate, preferably boiling above the boiling range ofgasoline, for example, boiling in the range of about 450 to 950 F., issubjected to hydrocracking at elevated temperatures and pressures in thepresence of a catalyst comprising a metal of the iron group which hasbeen incorporated into a silicaalumina hydrogel substantially free fromsodium.

Operating conditions employed in the hydrocracking conversion include atemperature in the range of about 500 to about 850 F., a hydrogenpartial pressure of about 750 to about 3000 p.s.i.a., a liquid hourlyspace velocity of about 0.2 to about 10, preferably 0.5 to 5, and ahydrogen-to-oil mole ratio of about 5 to about 50.

It is generally desirable to subject the hydrocarbon feed to a suitablepretreatment such as a relatively mild hydrogenation treatment, e.g., acatalytic hydrogenation treatment with a hydrogenation catalyst such ascobalt or nickel and molybdenum on alumina, silica-alumina, or othersuitable supports. An advantage of such a hydrogenation treatment is toremove from the feed cokeforming constituents which tend to deposit onthe hydrocracking catalyst and to remove impurities such as sulfur,oxygen, and nitrogen compounds which tend to lower hydrocrackingactivity and/or deposit on the catalyst. With most hydrocarbon oilsdesired as a hydrocracking feed, mild hydrogenation reduces the sulfurcontent to about 0.1% w. or less, prefably 0.05% w. or less, and theresidual nitrogen content to less than about ppm. w. and preferably lessthan 50 p.p.m. w.

In the hydrocracking process, feed is introduced to the reaction zone asa liquid, vapor or mixed liquid-vapor phase, depending upon thetemperature, pressure and amount of hydrogen mixed with the feed and theboiling range of the feed stock utilized. The hydrocarbon feed,including fresh as well as recycle feed, is introduced into the reactionzone with a large excess of hydrogen since the hydrocracking process isaccompanied by rather high consumption of hydrogen, usually of the orderof 500 to 2000 standard cubic feet of hydrogen per barrel of feedconverted. Conversion herein refers to the products obtained which boilbelow 420 F. Excess hydrogen is generally recovered, at least in part,from the reaction zone effluent and recycled to the reactor togetherwith additional makeup hydrogen. Pure hydrogen is not necessary as anysuitable hydrogen-containing gas which is predominantly hydrogen can beused. For example, hydrogen-rich gas containing on the order of 70% ormore hydrogen which is obtained from a catalytic reforming process canbe used. High purity gas is preferred, however, so as to use lower totalpressures.

Under normal conditions, total pressure employed in the hydrocrackingzone will be in the range of from about i 1000 to 3000 p.s.i.g. For agiven partial pressure of hydrogen in the reaction zone, total pressurewill depend upon such factors as purity of the hydrogen gas,hydrogen/oil ratio and the like. Too low a partial pressure of hydrogentends to decrease catalyst life.

The amount of iron group metal in the catalyst is generally expressed asa percentage of elemental metal based on the total weight of thecatalyst and can vary from about 0.1% to 14% by weight, usually not over8% by weight. Preferably the iron group metal is present in the catalystin the range of about 1 to by weight, and particularly active catalystsare obtained with about 2 to 7% by weight of iron group metal. Theamount of metal which is incorporated into the hydrogen will depend, ofcourse, upon the particular metal used. Nickel is especially active andis preferred.

The predominant portion of the catalyst is silica and alumina, which isgenerally referred to as the base for the catalyst. The catalyst basegenerally contains from about 40% to about 90% silica with theremainder, i.e., about 60% to 10%, alumina. A silica-alumina catalystbase having good cracking activity comprises from about 70% to 90%silica and from about to 10% alumina. While the silica-alumina is themost common and preferred base, other acid-acting refractory oxides,such as silica magnesia, silica alumina zirconia, silica-aluminaboria,and the like may be used if desired. These acidacting refractory oxidessuch as silica-alumina are generally known as primarily amorphousmaterials and are to be distinguished from the crystallinealumino-silicates known in the art as molecular sieves.

Any suitable method may be used for preparation of the silica-aluminahydrogel. For example, an aqueous solution of sodium aluminate is addedrapidly to a solution of sodium silicate in the proper proportions toprovide the desired concentration of silica and alumina in the catalyst.The pH of the mixture is brought to about 7 by the addition of a strongmineral acid, such as sulfuric acid, and the hydrogel is allowed to ageapproximately five minutes. The hydrogel is then washed with ammoniumsalt solution to eliminate, insofar as possible, sodium ions from thegel.

An alternative method of preparing silica-alumina hydrogel is to add amineral acid, e.g. sulfuric, to an aqueous solution of sodium silicateto adjust the pH to about 29 and then add, for example, aluminumsulfate. This is followed by neutralization with a base such as ammoniumor sodium hydroxide. The hydrogel is then washed with acidulated Water(e.g. demetallized Water) or ammonium nitrate solution to remove sodiumions.

The metal component is incorporated into the catalyst by contacting thehydrogel with an aqueous solution of iron group metal compound whereinthe iron group metal is present as a cation, for example, a metal saltsuch as the sulfates, nitrates or fluorides, the fluorides beingpreferred. Preferably the hydrogel is reslurried in the iron group metalsolution as this gives highly eificient contacting. Passing the irongroup metal solution through a filter cake of the hydrogel, such as thatobtained on a rotary drum filter or in a filter press, is sometimesineflicient owing to channeling of the solution through the filter cake.The hydrogel is generally washed with Water to remove excess solution,dried. and calcined, preferably in air, at a temperature of from about800 to 1200 F. Calcination temperatures of about 800 F. are generallyrequired to provide suflficient removal of bound water and ammonia fromthe catalyst. At temperatures above about l200 B, activity and stabilityof the catalyst tend to become adversely affected. Consequently,calcination temperature in the range from about 1050ll F. are preferred.

The mechanism by which a hydrogel such as a silicaalumina hydrogel takesup and holds an iron group metal is not clearly known. Silica-aluminahydrogel prepared by gellation of a solution of sodium silicate andsodium aluminate contains zeolitic sodium. In washing the hydrogel withammonium salts, sodium ions are replaced with ammonium ions. Ammoniumions can be exchanged with metal ions as disclosed in US. Pat.2,283,173. Ion-exchange is the general explanation since the metal ionsare retained in the gel even after the gel has been washed to remove themetal salt solution. However, While ion-exchange may be a mechanism bywhich metal ions are incorporated into silica-alumina hydrogel, it wouldappear that this may be only a partial explanation if at all.

Because of ease in filtering and other factors, silicaalumina hydrogelis conventionally prepared by precipitating silica hydrogel from sodiumsilicate solution followed by the addition of aluminum sulfate solutionto the silica hydrosol. Alumina is precipitated upon the silica by theaddition of sodium aluminate or ammonium hydroxide to raise the pH toabout 5. Sodium ions are removed from the silica-alumina hydrogel byWashing with demetallized Water which presumably leaves hydrogen ions atthe zeolitic sites. Such a hydrogel does not appear to be readilyamenable to ion-exchange with, for example, nickel. Since this hydrogelis formed under relatively acidic conditions, an appreciable amount ofsulfate ion is retained in the gel and it is possible that the sulfateion interfers with ion-exchange. Sulfate is conventionally removed fromsuch hydrogels by a treatment with a base such as ammonium hydroxide forpreparation of catalytic cracking catalysts. While the presence ofsulfate has not been shown to be detrimental to hydrocracking conversionreaction, the treated hydrogels retain nickel more readily. It ispossible that the nickel is retained as a complex with ammonia in thehydrogel. Thus, a clear explanation is not apparent, for nickel may beloosely sorbed by the hydrogel or may actually enter into exchange sitesin the hydrogel, or may be retained as a com lex with ammonia in thehydrogel. Upon calcination of the nickelcontaining hydrogel, the nickel,if not already interacted with the hydrogel, interacts with thesilica-alumina structure as any ammonia and structural water areevolved.

For use in hydrocracking conversion reactions, washing of themetal-containing hydrogel to remove excess metal solution can bedispensed with if desired since this eliminates a step in preparation ofthe hydro-cracking catalyst, reduces efiiuent problems, and thus resultsin cost savings. Metal remaining in solution is finely dispersedthroughout the hydrogel, and, although it may not provide a completelyreacted species, does not appear to be detrimental to the hydrocrackingconversion.

A catalyst highly active and stable for hydrocracking has from about 0.1to 5% by weight fluorine in addition to the iron group metal. Ingeneral, it is preferred that the atomic ratio of fluorine to nickel bein the range from about 1:1 to 5:1. The fluorine is incorporated intothe hydrogel prior to calcination of the hydrogel. Fluorine can beincorporated into the hydrogel as the hydrogel is formed, e.g., byincluding a fluoride salt in the solution from which the silica-aluminais gelled, or by treating the hydrogel with a fluoride compound before,after or simultaneously with incorporation of the iron group metal.Preferably the fluorine and iron group metal are incorporated into thehydrogel simultaneously from a common solution.

The fluorine and nickel apparently form a complex which is retained inthe hydrogel and is incorporated within the silica-alumina structure toprovide unusually high activity and stability. An explanation would seemto be that fluorine, unlike chlorine, readily forms a complex withnickel rather than a conventional electrolyte such as is the case withchlorine. Yet, the manner in which this complex enters or is held withinthe hydrogel is not known. It is possible that fluorine ions, which aresmaller than chlorine ions and which are about the same size as oxygenions, tend to replace oxygen ions in the silicaalumina structure and thenickel is held as a complex therewith. On the other hand, it may be thatthe nickel enters into zeolitic sites and the fluorine is held as acomplex therewith. This close association between the nickel and thefluorine to a great extent may result in the improved properties of thecatalyst. Upon calcination, the complex of nickel and fluorine mayinteract with the silicaalumina in such a manner so as to leave thenickel incorporated in the silica-alumina in a high valence state. Asfluoride ion is considered to be the best known ligand for stabilizationof the higher valence state of iron group metals, this may account forthe excellent stability of the catalysts of this invention.

Whatever may be the explanation, the incorporation of fluoride intosilica-alumina hydrogel is important for it apparently results in a morestable structure than that obtained with, for example, a conventionalfluoride-treated impregnated catalyst. Increased activity, if any,resulting from a conventional fluoride treatment of nickel impregnatedon precalcined silica-alumina is usually lost after only a few hoursuse, the activity eventually being about the same or less than animpregnated catalyst which has not been treated. On the other hand,incorporation of fluoride into silica-alumina hydrogel appears toenhance the elfectiveness of the hydrogenative component and of theacidic or cracking function. The presence of fluoride in the hydrogelapparently results in a more complete interaction of the metal ion, e.g.nickel ion, with silicaalumina gel, as a consequence of which a highlyactive and stable nickel-fluoro-silica-alumina structure is obtainedupon calcination of the hydrogel. Although a fluoride content of up toabout may be incorporated in the ionexchanged catalyst, there seems tobe little if any advantage in going above a fluoride content of about 3%by weight.

As stated before, nickel and fluorine can be incorporated into thehydrogel from a common solution. This is advantageous as it provideshighly eflicient uptake of nickel and fluorine into the hydrogel and anexcellent catalyst. In general, the atomic ratio of fluoride to nickelin the solution is in the range from about 1:1 to 5:1 and preferablyfrom about 2:1 to 4:1. The higher ratio is preferred as it tends topromote the formation of complex which seems to be highly effective forincorporation into the hydrogel. The pH of the solution should be in therange from about 4 to 7 as a higher pH tends to destroy the NiF (H O')complex and a lower pH greatly reduces uptake into the hydrogel.Commonly available compounds such as nickel fluoride, nickel nitrate,ammonium fluoride and the like can be used in preparing solutions of theabove properties. If desired, the hydrogel can be dried at lowtemperatures (about 250 F. or less) to remove substantially all or aportion of the sorbed Water before being contacted with the solution.

If desired, other promoters or other transitional metals, e.g., theGroup VIB metals or the platinum or palladium group metals, can beincorporated into the catalyst to provide improved properties of thecatalyst. The amount employed can vary over a wide range and depends, ofcourse, on the particular properties desired for a given hydroprocess.In hydrocracking, for example, activity and stability of nickel fluoroalumino silicate catalyst of this invention can be improved by theincorporation of minor amounts, i.e. about 0.1 to 5% by weight, oftungsten into the hydrogel. This is surprising since with impregnatedcatalysts of the prior art, tungsten-nickel has generally been found tobe more suitable for hydrotreating rather than hydrocracking whereinnickel catalysts are preferred. The role which tungsten plays whenincorporated in small amounts with nickel in silica-alumina hydrogel isnot clearly understood, but in general it appears that the amount oftungsten should be appreciably less on an atomic basis than the amountof nickel, e.g. less than about 0.5 and preferably less than about 0.2that of the nickel.

The transitional metals can be incorporated into the hydrogel separatelyfrom or together with the iron group metal. Thus, a silica-aluminahydrogel can be contacted by an aqueous solution containing one metaland then contacted with another solution containing the other metal orwith one solution containing both metals.

The catalyst apparently is an amorphous metal alumino silicatestructure, or an amorphous metal fluoro alumino silicate, as indicatedby various analytical techniques. For example, an ion-exchangednickel-fluoro-silica-alumina catalyst calcined at 9301020 F. wasdetermined to be paramagnetic, indicating the nickel to be present in anionic form. Yet, X-ray and electron diffraction examination revealed thecatalyst to be amorphous with no evidence of nickel oxide crystals.Further, the ion-exchanged catalyst is resistant to sulfiding onexposure to a sulfur environment. For example, an ion-exchanged nickelcatalyst exposed to a hydrogen sulfide containing gas (10 H /1 H S) at608 F. and used to hydrocrack 30 volumes of hydrocarbon (per volume ofcatalyst) containing 43 p.p.m. S was determined by X-ray examination tocontain little if any nickel sulfide structure. This indicates thatthere is little or no nickel oxide which at least under these particularconditions, is converted to crystals of nickel sulfide. With animpregnated nickel catalyst, prepared by impregnating precalcinedsilica-alumina (13% alumina) with nickel nitrate and calcining at 932F., X-ray diffraction examination indicates the catalyst to containlarge crystallites (approx. 400 A.) of nickel oxide. Upon exposure to asulfur environment, the impregnated catalyst is sulfided readily sincenickel oxide is substantially converted to nickel sulfide.

Compared with a nickel catalyst prepared by other methods such asimpregnation on calcined silica-alumina, the high activity of thepresent catalyst permits higher space velocities and/or lowertemperatures to be used for a given conversion with a given feed in ahydrocracking process. The use of high space velocities is advantageousin that reactor size and catalyst inventory can be lower, which isimportant from the cost standpoint, particularly in a high-pressureprocess.

Moreover, the superior resistance to nitrogen poisoning possessed by thepresent catalyst is quite advantageous in providing a practicalcommercial process. Most highboiling gas oil and cycle stocks availablein the refinery for conversion by hydrocracking generally have a highcontent of sulfur and nitrogen compounds. For example, a typicalcatalytically cracked gas oil boiling in the range of 500 F.-800 F.contains on the order of l to 2% w. sulfur and 400-600 p.p.m. w. totalnitrogen. The usual procedure is to hydrotreat these gas oils and cyclestocks with conventional hydrotreating catalysts to reduce the sulfurand nitrogen content of the oil. However, with a given catalyst, thereduction depends upon operating severity. For example, in pilot planthydrogenation studies at 700 F., 1500 p.s.i.g. and 20 moles hydrogen permole oil with a nickel molybdenum on alumina catalyst having a gooddenitrification activity, a space velocity of only 0.4 was required toreduce the total nitrogen content of the catalytically cracked oil toabout 25 p.p.m. w., whereas a space velocity of 0.1 was required toreduce nitrogen content to as low as 2 p.p.m. W. The higher severityrequired to obtain the lower nitrogen level adds greatly to the size andcost of a hydrotreating unit. Moreover, hydrogen consumption in reducingthe total nitrogen content to about 25 p.p.m. W. was only about 900s.c.f./bbl. compared with about 1300 s.c.f./bbl. in reducing the totalnitrogen content to 2 p.p.m. w. The increased hydrogen consumptionresults primarily from hydrogenation of aromatics at the higherseverity. In the subsequent hydrocracking operations, hydrogenconsumption is higher with a less hydrogenated gas oil feed than withthe severely hydrogenated gas oil. Even so, however, total hydrogenconsumption in the combination of hydrotreating and hydrocracking isgenerally lower with mild hydrotreating than with severe hydrotreating.This is an important consideration, especially where hydrogen is inshort supply and hydrogen generation facilities are required.

The effect of nitrogen compounds on hydrocracking catalyst performancedepends to a certain extent upon the type of the nitrogen compound andthus, in a practical sense, upon the nature of the feed. For example, ina homologous series such as pyridine, quinoline, and acridine, the rateof decrease of activity is related to the ratio of basicity of thecompound to the vapor pressure of the compound. On the other hand, evencertain relatively non-basic compounds, such as benzonitrile, are strongpoisons. Ammonia appears to be more of a cracking suppressor than apoison since catalyst activity levels off in the presence of ammoniainstead of decreasing continuously. In general, therefore, the nitrogencontent of a light feed such as light gas oil may be higher than that ofa heavy feed such as heavy gas oil. Moreover, the nitrogen content of astraight-run gas oil may be somewhat higher than a similar boilingcatalytically cracked gas oil, since a portion of the nitrogen compoundsin the straight-run gas oil seem to be innocuous or easily converted toless deleterious forms. Thus, while some feeds of quite high nitrogencontent may be hydrocracked, better results are obtained if the totalnitrogen content is reduced to below about 75 p.p.m. w. and preferablybelow 50 p.p.m. W.

EXAMPLE I Activity and stability of impregnated and the presentcatalysts Were determined in bench-scale hydrocracking of a hydrogenatedcatalytically cracked gas oil containing 2.2 p.p.m. N and 43 p.p.m. S. Acatalyst was prepared by rapidly adding a solution of sodium aluminateto a solution of sodium silicate, the relative proportions being such asto give about 28% alumina in the gel. Solution pH was brought to about 7by the addition of dilute H 80 The hydrogel which formed was washed withNH NO solution and water to remove substantially all sodium ions. Thewashed hydrogel was slurried with nickel nitrate solution (to provideapproximately 4% w. Ni in the catalyst) and then dried and calcined inair at 930 F.-l020 F.

An impregnated catalyst was prepared by impregnating pelletedsilica-alumina (25% A1 with nickel nitrate to provide 4.9% W. nickel,calculated as metal, in the fiual catalyst. The impregnated catalyst wasdried and calcined at 1020 F.

Each catalyst was separately tested in a bench scale hydrocracking unit.A stream of hydrogen was passed over the catalyst for three hours as thecatalyst was brought to the reaction temperature. In the case of theimpregnated catalyst hydrogen sulfide was included in the gas stream (10H /l H S) to convert the nickel oxide to nickel sulfide, a form which isknown in the art as a good hydrocracking catalyst. The gas oil feed wasthen 8 hydrocracked at 1500 p.s.i.g., 645 F., 4 LHSV and 10/1 molarratio of hydrogen to oil. An activity and stability index is obtainedfor each catalyst, as determined by refractive index data which isindicative of conversion to gasoline and lower boiling products.Activity index corresponds to the conversion at 3 hours time in theprocess period. Stability index is the percent of retention of activityafter a decade of running, e.g., indicated activity at 10 hours as apercent of activity at one hour. Activity and stability of theion-exchanged catalyst was 69 and 54, respectively, whereas the activityand stability of the impregnated catalyst was 31 and 60, respectively.

EXAMPLE II The effect of fluoride on properties and performance of acatalyst comprising nickel incorporated into silicaalumina hydrogen isdemonstrated by the following experiments. Nickel catalysts(approximately 4% W. Ni) with and without fluoride were preparedaccording to the method described in Example I. To incorporate fluorideinto the silica-alumina hydrogel, sodium fluoride Was added to thesodium aluminate solution in an amount to provide 1.8% W. F in the finalcatalyst. Bench-scale hydrocracking tests were made in the manner andwith the feed as described in Example I. The catalyst containing nofluoride had a density of 0.82 g./ml., an activity of 69 and a stabilityof 54. The catalyst containing fluoride had a density of 0.91 g./ml., anactivity of 98, and a stability of 65.

EXAMPLE III Comparative experiments with an ion-exchanged catalyst andimpregnated catalysts demonstrate a marked superiority of theion-exchanged catalyst for conversion of relatively highnitrogen-containing feeds. A nickel catalyst Was prepared according tothe procedure described in Example I except that fluoride wasincorporated into the silica-alumina hydrogel by adding sodium fluorideto the sodium aluminate solution before it was added to the sodiumsilicate solution. The catalyst, containing approximately 3.7% w. Ni and1.8% W. F, was dried and calcined at about 1100 F.

An impregnated nickel catalyst was prepared by pelleting a commercialsilica-alumina (25% A1 0 cracking catalyst using a stearic acid (2% W.)as binder. The pelleted catalyst was calcined at 930 F. to burn out thebinder before being impregnated with an aqueous solution of nickelnitrate. The impregnated catalyst was dried and calcined at 1420 F. Thefinal catalyst contained 5.5% W. nickel calculated as metal.

An impregnated tungsten-nickel catalyst was prepared from commercialsilica-alumina (app. 25% A1 0 Extruded pellets of the silica-aluminawere impregnated with an aqueous solution of nickel nitrate, ammoniummetatungstate, and ammonium bifiuoride, dried and calcined. The finishedcatalyst contained 11.7% w. Ni, 18.8% w. W and app. 33% w. F.

The impregnated and ion-exchanged catalysts were separately tested foran extended period of time in hydrocracking mildly hydrogenatedcatalytically cracked gas oil having typical properties given below:

ASTM distillation, F.:

IBP 360 5% 530 563 595 613 629 643 657 673 690 86% 700 Sulfur, p.p.m. w.210

Total nitrogen, p.p.m. W. 23

In the test procedure the catalyst was placed in the reactor vessel andheated to the desired initial reaction temperature over a period ofabout three hours while passing therethrough a stream of hydrogen gas.In the case of the impregnated catalysts, hydrogen sulfide was includedin the hydrogen gas H /l H S) to convert the nickel oxide to nickelsulfide. Hydrogenated catalytically cracked gas oil and hydrogen werethen continuously charged to the reactor. Reactor pressure wasmaintained at 1500 p.s.i.g. Temperature was adjusted as necessary tomaintain conversion to gasoline and lower boiling products at 60 to 65%w.

With the impregnated nickel catalyst, the starting temperature for thegas oil feed was 590 F. at a liquid hourly space velocity (LHSV) of 1and a hydrogen/oil ratio of 40/1. Catalyst decline under theseconditions was quite rapid so that frequent temperature increases werenecessary to maintain conversion as the run progressed. As thetemperatre became higher, catalyst decline rate became even more severeand it became difiicult to maintain conversion, which varied between 55%to 65%. Therefore, after only 120 hours operation, during which the timetemperature had been increased to 698 F., space velocity was reduced to0.67. After a brief interval of fairly steady operation, catalystactivity soon began to decline again at a rapid rate. The temperaturehaving reached 725 F. after an additional 190 hours of operation, therun was terminated. Total catalyst life to 750 F. reaction temperaturewas determined to be only 450 hours by extrapolation of the catalystdecline rate as determined from a graph of time in hours, on alogarithmic scale, against temperature demand.

With the impregnated tungsten-nickel catalyst, a space velocity of 0.67and a H /oil ratio of /1 were maintained during the entire operation.Catalyst decline for this catalyst, even under the relatively low spacevelocity, was quite rapid. As temperature became higher, catalystdecline rate became even more severe. The temperature demand was 696 F.after only 8.5 days and 743 F. after days, when the operation wasterminated.

With the ion-exchanged catalyst, the starting temperature for the gasoil feed at an LHSV of 1 was approximately 535 F. The markedly lowertemperature requirement for 60 to 65% conversion was indicative of amore active catalyst. Hydrogen/oil ratio was maintained in the range of15/ 120/ 1. Operation was relatively steady with only slight periodictemperature increases required to maintain conversion. A temperaturedemand of only 680 F. after approximately 1500 hours operationdemonstrates the excellent stability of the ion-exchange nickelcatalyst.

EXAMPLE IV A silica-alumina hydrogel for catalysts of this invention isprepared by diluting 376 gms. sodium silicate (27.0% SiO to 2400 ml.with distiled water. The sodium silicate solution is triturated to pH9.0 with 3 molar H 80 and the gel which forms is aged 10 minutes. Analuminum sulfate solution consisting of 209 gms.

in 1000 ml. water is added to the gel with rapid stirring. The pH of thesolution is raised from about 3.0 to 5.0 by the addition of 3 molar NHOI-l to precipitate alumina. The resulting silica-alumina gel isfiltered and washed with acidulated water (H SO pH of 3) to removesodium ions and dilute ammonium hydroxide to remove sulfate 10118.

Washed hydrogel was slurried in an aqueous solution containing 30.0 gms.Ni(NO -6H O and 10.3 gms. NH F and left for four hours. The hydrogel wasfiltered, washed with water, dried at 248 F., and calcined attemperatures up to about 1100 F. The finished catalyst contained 3.8% w.nickel and 2.9% w. fluorine.

Another catalyst was similarly prepared by contacting drotreated. Thehydrotreated oil had the following properties:

Gravity, API 25.2 Sulfur, percent w 0.038

Nitrogen, p.p.m. w 23 ASTM dist., F.:

IBP 500 10% 612 30% 650 50% 679 68.5% 700 The hydrotreated oil washydrocracked at 1500 p.s.i.g., 10/1 H /oi1, and 0.67 LHSV. Temperaturewas controlled to maintain 65% v. conversion to products boiling lessthan 420 F.

The nickel catalyst was less active and less stable than thetungsten-nickel catalyst as indicated by the temperature required tomaintain conversion. After about 290 hours operation, the nickelcatalyst required a temperature of 659 F. whereas the tungsten-nickelcatalyst required a temperature of only 646 F. Moreover, the nickelcatalyst steadily declined in activity as indicated by a temperaturerequirement of 671 F. after 565 hours and 684 F. after 740 hoursoperation. In contrast, activity of the tungsten-nickel catalyst wasrelatively constant, a temperature of only 649 F. being required after565 hours.

EXAMPLE V A nickel catalyst was prepared by slurrying silica-aluminahydrogel (app. 20% alumina and substantially free from sodium ions) inan aqueous solution of nickel nitrate and ammonium fluoride toincorporate nickel and fluoride ions into the hydrogel. The hydrogel wasthen washed, dried and calcined. The finished catalyst contained 4.4% w.nickel and app. 2.5% w. F.

A tungsten catalyst was prepared by mulling 1333 gms. of silica-aluminahydrogel (app. 25% W. alurnina and substantially free from sodium ions)with 80.0 ml. of solution containing 30.6 g. (NH W O -8H O and 6 gms. NHHF followed by drying and calcining the finished catalyst contained 8.5%w. W and 1.8% w. F.

Source of the feed material used in this example Was a heavycatalytically cracked gas oil having the following properties:

Gravity, API 23.2 Sulfur, percent w. 1.35 Nitrogen, p.p.m. w. 516 ASTMdist., F.:

IBP 532 10% 612 30% 648 50% 670 70% 694 74.8% 700 The gas oil washydrotreated to provide a hydrocracking feed containing 200 p.p.m. w. Sand 0.5 p.p.m. w. N. The hydrotreated oil was hydrocracked at 1200p.s.i.g. 15/1, H /oil, and 0.67 LHSV using each of the above catalysts.Temperature was adjusted as necessary to provide 62% w. conversion toproducts boiling less than 420 F. With such a feed of low nitrogencontent, the nickel catalyst was quite active and stable. A temperatureof only 583 F. was required after 250 hours operation when operation wasterminated. Activity of the tungsten catalyst was considerably less thanthe nickel catalyst as indicated by a temperature demand of 622 F. at250 hours operation, and despite the low nitrogen content of the feed,activity of the tungsten catalyst steadily decllned.

EXAMPLE VI A co-gelled catalyst was prepared by mixing aqueous solutionsof sodium silicate, sodium aluminate and sodium fluoride and then addingto the mixture an aqueous solution of nickel nitrate at such a rate thatall of the nickel nitrate solution was added by the time the solutionwas completely gelled. Solution pH was brought .to about 7 by additionof dilute H 50 The hydrogel was then allowed to age for about 5 minutes,after which it was washed with ammonium nitrate solution and water toremove substantially all of the sodium ions. The washed hydrogel wasdried for approximately hours at 248 F. (120 C.), crushed, sized, andcalcined at 930 to 1020 F. for about 4 hours. The final catalystcontained about 3.6% w. nickel, calculated as metal, and approximately1.8% w. F., with about 28% alumina in the base.

A catalyst was similarly prepared but instead of adding nickel nitratesolution as the silica-alumina hydrogen was being formed, the hydrogelwas slurried in nickel nitrate solution to ion-exchange nickel into thehydrogel. The nickel content of the ion-exchanged catalyst wasapproximately 3.6% w. The ion-exchanged hydrogel was then dried, crushedand calcined as described above for the cogelled catalyst. Theion-exchanged and co-gelled nickel catalysts were separately tested in abench scale hydrocracking unit under identical conditions. A mixture ofhydrogen and hydrogen sulfide (10 H /1 H 8) was passed over the catalystfor three hours as the catalyst was brought to reaction temperature.Hydrocracking was carried out with the feed and under conditions asdescribed in Example I. Activity and stability of the co-gelled catalystwas 83 and 62, respectively, whereas activity and stability of theion-exchanged catalyst was 94 and 69, respectively. Catalyst density of0.93 g./cc. for the ion-exchanged catalyst was somewhat higher than the0.82 g./ cc. obtained for the co-gelled catalyst.

EXAMPLE VII TABLE I Catalyst preparation Imprcg- Hydro- Hydrogel, nated,gel, 4.4% Ni, 1.5% F 2.4% F approx. 3% F Pressure, p.s.i.g 1, 200 1, 2001, 200 Temperature, F 450 550 451 LHSV 1. 0 1.0 1.0 Conversion, percentIt can be seen that of itself, fluorine incorporated into silica-aluminahydrogel results in an activity little better than that of impregnatedfluorine despite a much higher temperature. In contrast, incorporationof nickel, a hydrogenation component, with the fluorine into thehydrogel results in a highly active catalyst.

EXAMPLE VIII A silica-alumina hydrogel was prepared according to theprocedure given in Example IV. Approximately 1600 grams of hydrogel(about 810% solids) was slurried in two liters of an aqueous solutioncontaining 14 grams 12 NiF -4H O and 7 grams NH F and having a pH of6.1. Uptake of nickel from the solution by the hydrogel was virtuallycomplete. When a solution containing only the nickel fluoride was used(pH of 5.8), uptake of nickel was about 85%.

EXAMPLE IX In another embodiment of the invention a cobalt hydrocrackingcatalyst is prepared in a manner similar to that described in ExampleIII. A silica-alumina hydrogel, after being washed with ammonium nitratesolution and water to remove sodium ions, is slurried in a solution ofcobalt nitrate. The hydrogel is then filtered, washed, dried, andcalcined in air at 1100 F. The cobalt catalyst is active and quitestable in the hydrocracking of hydrogenated gas oil boiling in the range450-650 F. at 650 F., 2 LHSV, 1500 p.s.i.g., and 15/1 hydrogen/oil moleratio.

EXAMPLE X To demonstate the effect of calcination temperature, ahydrogel of silica-alumina (approximately 22% w. alumina) was preparedand washed to remove sodium and sulfate ions. The washed hydrogel wassoaked in a solution containing nickel nitrate and ammonium fluoride,after which it was given another wash to remove excess solution. Theuptake of nickel and fluoride was suflicient Surface Calcination area,temp, F. mfl/g.

These catalysts were tested individually for hydrocrackinghydrodenitrified catalytically cracked heavy gas oil. Typical propertiesof the hydrocracker feed are as follows:

Mol wt 247 Nitrogen, ppm 1 Sulfur, p.p.m 40-60 Aromatics, millimoles/gms 136-166 The hydrocracking was conducted at 1500 p.s.i.g. totalpressure, 15/1 H /oil, and 1 LHSV. Temperature was periodically adjustedas necessary to maintain conversion at about 67% w.

With Catalyst A, activity and stability were very good. Activity declinerate was only 0.60 F./day when operations were terminated at the end of685 hours. Catalyst B was only slightly less active in the temperaturerequire ment to maintain conversion was about 6 F. higher than that forCatalyst A. Activity decline rate was about the same as for Catalyst A.With Catalyst C, however, the activity decline rate was noticeablyhigher. After some 450 hours operation. Catalyst C began to deactivateat an increasing rate. Operation with Catalyst C was terminated at theend of about 570 hours, the catalyst decline rate being 2.75 F./day overthe final hour period.

The loss in activity and stability at high calcination temperatures isquite surprising, considering that it is taught in the art thatcatalysts wherein nickel is impregnated on silica-alumina are improvedin activity at very high calcination temperatures on the order of1300-1475" F. (about 700800 C.) (see British Pat. 917,469 or CanadianPat. 683,239). To determine the activity of an impregnated catalystcalcined at high temperatures, a catalyst was prepared by pelletingspray dried silicaalurnina (25% w. alumina) calcining at 1020" F. toburn out the binder (stearic acid), impregnating with fluoride, drying,impregnating with nickel nitrate, and calcining at 1418 F. (770 C.). Thefinal catalyst,

which contained 5.5% w. nickel and 3.1% W. fluorine was sulfided at 608F. with a mixture of hydrogen and hydrogen sulfide (10/1 H /H and testedunder the hydrocracking conditions given above. Activity and stabilitywere very poor and the operation was terminated at the end of about 250hours with a temperature demand of 698 F. Activity decline rate for thelast 145 hours was 16.7 F./day.

EXAMPLE XI A hydrogel of silica-alumina (approximately 22% w. alumina)was prepared and washed to remove sodium and sulfate ions. The washedhydrogel was soaked in a solution containing ferric nitrate and ammoniumfluoride to give about 8% w. iron and 3% w. fluorine in the finalcatalyst, after which the hydrogel was given another wash to removeexcess solution. Thecatalyst was calcined at This catalyst was treatedwith a mixture of hydrogen and hydrogen sulfide (1011 H /H at 608 F. andwas used to hydrocrack a catalytically cracked heavy gas oil,hydrotreated to 3 p.p.m. N. Hydrocracking conditions were 1500 p.s.i.g.,15/1 H /oil mol ratio, and 0.67 LHSV. Temperature was adjusted asnecessary to maintain con version at about 65-67% w. Activity andstability of the catalyst was quite good as shown by an increase in atemperature demand from 586 F. at 65 hours to 599 F. at 141 hours.

A catalyst containing tungsten in addition to iron was prepared in asimilar manner by including ammonium metatungstate in the solutioncontaining the ferric nitrate and ammonium fluoride. The final catalystcontained 2.7% iron, 3.5% W. tungsten, and 2.5% w. fluorine. When testedin the manner described above, activity and stability were substantiallythe same as for the iron catalyst. Activity declined from 586 F. at theend of 50 hours to only 606 F. at the end of 300 hours, at which timemechanical difliculties were encountered which soon necessitatedtermination of the experiment.

Catalysts prepared by impregnating iron onto previously calcinedsilica-alumina cracking catalyst are so low in activity and stability asto be impractical.

I claim as my invention:

1. A catalyst suitable for hydrocracking hydrocarbon oils whichcomprises from about 0.1% to 14% by weight of an iron group metal andabout 0.1% to 5% by weight fluorine incorporated into an amorphousacid-acting refractory oxide, said incorporation being eflected bycontacting a hydrogel of the acid-acting refractory oxide substantiallyfree from sodium with an aqueous solution of an iron group metalcompound wherein the metal is present as a cation, washing the contactedhydrogel to remove unreacted iron group metal, and calcining saidcontacted hydrogel at a temperature of about 800 to 1200 F., saidfluorine being incorporated into the hydrogel prior to calcination.

2. A catalyst suitable for hydrocracking hydrocarbon oils whichcomprises from about 0.1% to 14% by weight nickel and about 0.1% to 5%fluorine incorporated into amorphous silica-alumina, said incorporationbeing effected by contacting silica-alumina hydrogel substantially freefrom sodium with an aqueous solution of a nickel compound wherein thenickel is present as a cation, washing the contacted hydrogel to removeunreacted nickel, and calcining said contacted hydrogel at a temperatureof about 800 to 1200 F., said fluorine being incorporated into thehydrogel prior to calcination.

3. A catalyst suitable for hydrocracking hydrocarbon oils whichcomprises from about 1% to 10% by weight nickel and about 0.1% to 5% byweight fluorine incorporated into amorphous silica-alumina having fromabout 40% to by weight silica, said incorporation being efiected bycontacting a hydrogel of the silica-alumina substantially free fromsodium with an aqueous solution containing a fluoride compound and anickel compound wherein the nickel is present as a cation, the atomicratio of fluoride to nickel in said solution being in the range fromabout 2:1 to 4:1 and the pH of the solution being in the range fromabout 4-7, washing the contacted hydrogel to remove unreacted nickel,and calcining the contacted hydrogel.

References Cited U.S. Cl. X.R. 252441, 453, 455, 458

